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Publikacije (21)

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S. Hanjalic, V. Helać, Merisa Hanjalić, Nedim Hasanbegovic

Energy production is one of the most crucial scientific, technological, economic, and political challenges in today's world. In response to the increasing demands of the European Union for reducing CO2 emissions and mitigating climate change, countries are obligated to align their national energy plans with clearly defined objectives, aiming for climate neutrality by 2050. This paper explores the location potential and optimal implementation of biomass power plants in Bosnia and Herzegovina. Biomass power plants, particularly those utilizing wood and plant biomass, are a promising solution for simultaneously reducing pollution, addressing unnecessary waste, and improving the energy efficiency of the systems where they are installed. The paper concludes that the potential of wood and plant biomass in Bosnia and Herzegovina remains underutilized. From an eco-perspective, the paper will also examine the reuse of large degraded areas in mines, where the fast-growing energy crops like Miscanthus could be planted.

Kenan Suljic, V. Helać, Merisa Hanjalić, S. Hanjalic

Recognizing the increasing importance of renewable energy sources, specifically wind farms, in today's power environments, this paper aims to clarify the complex interactions between these renewable energy facilities and distribution grids functioning under low-demand conditions. This particular case comes with inherent limitations that must be considered by taking into account all the factors that can influence the performance of the wind farm under these conditions. The modelling procedure and the simulation of the connection of the wind farm to the power system in rural area was performed using EMTP-RV software. The mean annual production of the wind power plant and the behaviour of the wind power plant in the event of failure in a real power system were calculated. Also, the power quality was examined in agreement with the Network Code of the transmission system of Bosnia and Herzegovina.

The contribution of renewable energy sources to the power system stability will have to be greater in the future. The problem will arise if the share of wind power plants in total production increases and large failures occur. Then, wind farms, which are often called inertia-less sources in the literature, will have to help maintain the frequency in a normal amount by changing the management method and based on fast PMU measurements. This can be done by using the synthetic inertia size, which is defined for sources that are derived from the system via energy converters and which do not participate in defining the total inertia of the system. This paper provides a better insight into the understanding of the concept of synthetic inertia, as well as insight into the current development of management and the application of synthetic inertia in maintaining the stability of the power system.

The increase in the number of wind farms and their share in the total electrical energy generation leads to the need for a different approach to this source in cases where the stability of the power system is potentially impaired. With the development of different types of wind power plants, equipped with power electronics devices, there is the possibility of quick power management and injection, in conditions when it is needed, where a huge amount of accumulated kinetic energy can also be used. This paper presents the influence of a wind power plant equipped with a full-scale converter on the transient stability in cases of close and distant short circuits, during the outage of a heavily loaded line. Special attention was paid to the Rate of Change of Frequency (RoCoF) in the power system in cases with and without a wind farm where fast power injections were possible.

Amer Čerkez, S. Smaka, S. Hanjalic, V. Helać, Merisa Hanjalić

Climate problems, the increasingly robust European emissions policy and falling prices of solar and wind have led to the shutdown of many thermal power plants and increased installation of renewable energy power plants. The installed capacity of wind and solar power plants in our country is not yet significant, but small hydropower plants are often considered as a good solution for the power supply to remote areas despite the problems that sometimes arise after the installation of these power plants. This paper describes a power quality problem of high voltages occurs after the installation of a small hydropower plant of 800 kVA in an area with predominantly industrial consumers. Many industries use high technology for manufacturing and require high power quality and reliability of power supply. Even modest power quality problems can have significant technical and economic effects on these consumers. Therefore, it was necessary to precisely monitor power quality to adequately address all related problem recorded during the plant performance test phase. Also, the observed problem has led to power plant outage on several occasions in a short period of time which resulted in a reduction in power generation. Techniques for mitigation the observed power quality issue are also considered in this paper. The implemented solution of the problem is verified by power quality monitoring and SCADA system measurements.

The steady increase in electricity demand has led to more installed generation capacity in wind farms, which, due to the stochastic nature of their production, may have characteristic and non-standard responses to some occurrences in the grid. The power output from the wind farm changes constantly, depending on the wind speed, so the impact of the network on the wind farm will inversely vary depending on the moment of the short circuit and the wind farm operating mode, since the values of currents and voltages in these fault systems depend on the power flows. Although wind power is known to contribute to the short circuit current / power at the point of its connection, this paper focuses on the response of the wind farm to short circuits in the network and the impact of these phenomena on the grid-wind relation. The aim of the paper is to determine the worst type of short circuit for wind turbine operation in the distribution system.

V. Helać, S. Hanjalic, Semra Curevac-Helac

Depending on actual load profiles connected to grid containing a PV system, losses and power quality disturbances vary during the day due to the power unbalance in the connection node. With the increase in size of PV power plants this problem becomes more important. Different load profiles have different correlation with the daily power generation from the PV system. Therefore, economic and technical impact of different daily load curves on grid connected PV systems should be considered. This paper gives an analysis of aforementioned problems. After the description and comparison between different load profiles and daily load curves, a simulation model is described and different situations of occurring problems are tested and analyzed. Simulations were carried out with real load profiles. Finally, this paper gives an overview of problems and gives few proposes for their solution.

V. Helać, Haris Capelj, V. Becirovic, S. Hanjalic, I. Pavić

Analysis of harmonic propagation in transmission network represents an important factor in exploitation of the power system. These analyses are conducted in time and frequency domains. In a case of a robust power system, analyses are usually conducted in frequency domain and usually carried out in the Three-phase system (TPS), so that all effects of interest in the frequency spectrum are taken in consideration. Transmission line (TL) modeling in TPS and frequency domain, with the usage of Kron Matrix Reduction (KMR), can be found in this paper. The model is created for frequency values between 0.05 (Hz) and 10 (kHz), which represent the frequency spectrum of interest. Mathematical procedure for implementing the KMR can also be found in this paper. Usage of KMR for voltage profile analysis on a TL is shown on a plain example. The proposed model is compared with tested mathematical models from EMTP-RV.

V. Becirovic, V. Helać, S. Hanjalic, S. Smaka, H. Šamić

The paper describes a photovoltaic system (PVS) composed of a group of photovoltaic (PV) panels and presents the initial evaluation of power quality (PQ) in the low-power microgrid connected to these PV panels. This PVS is called solar tree and it is built as a research platform at our faculty to conduct teaching and research on renewable energy sources. The solar tree can operate in two modes: on-grid and off-grid (autonomous operation). An off-grid mode was analysed and experiments were carried out in order to determine the maximum power that can be delivered to the load connected to this autonomous photovoltaic system (APVS). Also, the various consumer's responses to a sudden load changes in this APVS were analysed. The experiments were carried out by using modern power quality monitoring devices and PQ of this single-phase APVS with energy storage is examined in terms of compatibility with the relevant international standards.

V. Becirovic, S. Smaka, Roko Jerčić, S. Hanjalic, V. Helać

Phasor estimation is an essential task in power system since the voltage angle and voltage RMS determine the available active power and its flow. This paper proposes fast and simple algorithm for harmonic phasor estimation in a three-phase system. Harmonics are considered the most serious power quality (PQ) problem in the emerging scenario with a growing proportion of power electronic based devices in the power system. The algorithm is based on well-known mathematical transform and recommendations given in relevant IEC and IEEE standards. The presented algorithm can be used to generate input data for Harmonic State Estimation.

A. Maksumic, V. Becirovic, S. Hanjalic, H. Šamić, S. Maksumic

Construction of photovoltaic (PV) power plants should be techno-economically justified. In this paper, two types of PV systems are considered: (1) systems with fixed installed modules and (2) dual axis tracking systems (trackers). Two analyses have been carried out for the aforementioned systems: (1) designing PV systems using PVGIS tool and (2) real measurements of two PV systems. Based on these analyses and comparison of their results, and taking into consideration the required investment for construction, a conclusion was made on the profitability of such projects. This research was conducted according to the currently valid legal regulations and incentives in the Federation of Bosnia and Herzegovina (FBiH).

V. Helać, H. Šamić, S. Hanjalic, B. Nikolic

Solar cells are the main candidate for the replacement of conventional energy sources, because they can provide almost permanent power at low cost and almost no pollution. In this paper, an organic solar cell with an active layer made of P3HT and PCBM material is considered and the effect of the active layer thickness on the efficiency of photovoltaic conversion. Furthermore, the efficiency of the energy conversion of the organic solar cell and conventional silicon cells was compared. Finally, optimal thicknesses of the active layer and the layer for rejecting minority carriers are chosen.

Many renewable energy sources are not able to provide the demanded electrical energy during the day. This problem is getting more important with the increase of power plants which are based on renewable energy. The proposed method for overcoming the aforementioned problem is the building of hybrid power plants with two or three different energy sources. The most common hybrid power plants are solar-wind power plants, who produce electricity by using the complementary characteristics of solar irradiation and wind speed. The hybrid solar-wind power plants contain a lot of power electronic devices that affect the power quality disturbances. Therefore, an analysis of the dynamic of such power plants is necessary. First part of this paper presents the modeling of hybrid solar-wind power plants. The second part analyzes the impact on power quality of hybrid solar-wind power plant during its daily working cycle.

Renewable energy sources in addition to all the advantages over the non-renewable energy sources have a lot of limitations, where the biggest of them are the price and the inability of constant electricity generation. One way of overcoming the problem of inability of constant electricity generation is to build hybrid power plants with renewable energy sources. This primarily highlights hybrid solar - wind power plants, which produce electricity by using solar radiation and wind energy. Since the hybrid solar - wind power plants consist of a photovoltaic power plant and a wind power plant and are usually constructed as a distributed source, it is necessary that the regulatory frameworks define criteria and actions for the connection of a hybrid solar - wind power plant in the power system. This paper gives a short overview of criteria and actions for the connection of a hybrid solar - wind power plant in the power system according to official documents in Bosnia and Herzegovina.

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